Electrically-heated paper drying drum



March 8, 1966 A. PRICE 3,239,652

ELECTRICALLY-HEATED PAPER DRYING DRUM Filed July 9, 1963 2 Sheets-Sheet 1 INVENTOR Aer/nae 7 /8/65 March 8, 196 6 A. PRICE 3,239,652

ELECTRICALLY-rHEATED PAPER DRYING DRUM Filed July 9, 1963 2 Sheets-Sheet 2 I NVENTOR. Aver /e 29/45 @mwdj United States Patent 3,239,652 ELECTRICALLY-HEATED PAPER. DRYING DRUM Arthur Price, 9 Highland Ave., Great Neck, N.Y. Filed July 9, 1963, Ser. No. 293,626 4 Claims. (Cl. 219-469) This invention relates to drying apparatus for sheet materials; more particularly, this invention relates to paper drying apparatus and methods for manufacturing and maintaining such apparatus.

Apparatus presently used to dry paper and other sheet materials is costly, inefficient, slow, and expensive to main tain and operate. For example, in the manufacture of paper, the equipment used to dry the newly formed paper sheet has all of these deficiencies. The paper sheet usually is passed over a relatively large-diameter heated drum which is known as a Yankee drum, and then over a series of smaller heated drums. These drums heat the material and cause the moisture in it to evaporate.

Each drum is heated by high-pressure, super-heated steam which is fed into its interior. Typically, these drums are made of cast-iron or steel and must have relatively thick walls capable of withstanding the high pressure of the super-heated steam. In addition, each drum must be carefully inspected to ensure that it meets the high specifications set for boiler structures by governmental authorities. Further, the outside surface of the drum must be given an extremely smooth finish so that the paper passed over the surface will be smooth.

A major disadvantage of such drums is that they are expensive. Provision of the thick walls, the smooth exterior finish, and the costly inspections makes these drums expensive to manufacture. Furthermore, a system using such drums is expensive to operate since the generation of high-pressure super-heated steam is a costly process. This expense is increased by the substantial heat loss in the thick walls of the drum. In addition, some of the steam condenses and forms water inside the drums, and costly and complex equipment must be provided for removing this water.

In order to set the drying rate of the drums at an optimum, the temperature of each drum must be maintained at a certain predetermined value. It is difficult to control the temperature of each drum when steam heating is used.

The paper, as it emerges from the manufacturing process, contains a liquid which may be either highly acid or alkaline. This liquid attacks the exterior surfaces of at least the first few of the metal drums in the series of drying drums and corrodes and pits these surfaces. Since these pitted and corroded surfaces are too rough to use in paper making, they must be resurfaced periodically. For example, it is common practice to remove one or more drums from the system once each year and have its surface ground and polished in order to make it smooth enough for further use. This resurfacing forces the shutdown of the paper making facilities and slows down the rate at which paper can be produced. Furthermore, it is expensive to resurface these drums so often.

Accordingly, it is an object of this invention to provide sheet material drying apparatus that is relatively inexpensive to manufacture and operate, and requires a minimum of maintenance.

Another object of this invention is to provide paper drying apparatus which does not use steam and thus avoids the expense and complications provided by its use.

A further object of this invention is to provide a paper drying drum which is relatively inexpensive to manufacture, inexpensive to operate, and whose surface does not require frequent refinishing and the consequent manufacturing shut-downs and slow-downs caused by such refinishing.

3,239,652 Fatented Mar. 8, 1966 Still further, an object of this invention is to provide paper drying apparatus incorporating a plurality of heated paper drying drums each of whose temperature is easily and automatically controlled.

Another object of this invention is to provide an improved method for resurfacing used paper-drying drums.

The drawings and descriptions that follow describe the invention and indicate some of the ways in which it can be used so as to meet the above-stated objects. In addition, some of the advantages provided by the invention will be pointed out.

In the drawings:

FIGURE 1 is a perspective, partially cut-away view of a drying drum constructed in accordance with the present invention;

FIGURE 2 is a perspective, partially cut-away view of another drying drum constructed in accordance with the present invention;

FIGURE 3 is a perspective, cut-away view of still another drying drum constructed in accordance with the present invention;

FIGURE 4 is a schematic diagram of paper drying apparatus constructed in accordance with the present invention;

FIGURE 5 is a schematic circuit diagram showing the electrical connections for the paper drying apparatus shown in FIGURE 4.

The drying drum 10 shown in FIGURE 1 includes a cylinder 12 made of electrically non-conductive material with a plurality of resistive heating elements 14, each of which is imbedded in the material and has both of its ends exposed. Cylinder 12 preferably is made of ceramic material sold under the trademark Pyrocerarn by Corning Glass Works, Corning, New York. Alternatively, this cylinder can be made of glass or materials commonly used to make electrical-heating panels. These materials, and especially ceramic materials such as Pyroceram," have highly desirable qualities for use in such a drying drum. They are extremely hard and resistant to scratching, and many of them, such as Pyroceram, have high structural strength. They have very good electrical characteristics and are ideally suited for electrical-heating applications. Furthermore, these materials are highly resistant to pitting, corroding, or other damage that might be caused by acids or other corrosive materials.

The resistive elements 14 preferably are made of Nichrome wire but may be made of other well-known resistive materials.

Two circular end plates 16 and 18 are secured to the ends of cylinder 12. End plates 16 and 18 have flanges 20 and 22, respectively, which extend toward one another in the direction of the longitudinal axis of the drum 10. These flanges are spaced radially inwardly from the outer edge of end plates 16 and 18 so that the outer edge portions 24 and 26 of disks 16 and 18 make electrical contact with the exposed ends of heating elements 14. Cylinder 12 may be secured to flanges 20 and 22 by use of any of a number of well-known adhesives. Permanent electrical contact may be made between end plates 16 and 18 and heating elements 14 by welding them together, or by first butt-welding a relatively thin metal strip over the exposed ends of elements 14 and then welding the relatively thicker rim portions 24 and 26 of the end plates to this metal strip. The flange portions 22 may be extended towards one another to provide additional structural strength for the drum, if desired.

End plates 16 and 18 each have metal hubs 28 and 30 and shafts 32 and 34 secured, respectively, to plates 16 and 18. Shaft 32 turns in a bearing block 36 and shaft 34 turns in another bearing block 38. The drum 10 may be rotated by driving either shaft 32 or shaft 34 with any desired type of rotary drive source.

An electrical lead 42 is connected to one end of each of the resistive heating elements 14 through bearing block 36, shaft 32, hub 28 and end plate 16. Similarly, an electrical lead 40 is connected to the other end of each of the resistive elements 14 through bearing block 38, shaft 34, hub 38, and end plate 18. Leads 40 and 42 are connected to a standard AC. or D.C. power supply to energize heating elements 14 and cause them to heat the surface of the drum 16. Electrical control equipment also is connected to leads 40 and 42, as will be described below.

Drum has many advantages over drying drums previously used. First, since steam is not used to heat drum 10, the disadvantages inherent in the steam-heated drum are avoided. For example, the walls of the drum need not be as thick as in previous drums since they need not withstand high steam pressures. Thus, a saving in materials is accomplished. Further, the expense of meeting governmental steam boiler codes is avoided. Still further, this drum is much lighter and easier to handle than previous drums. The power required to drive it and the bearing load requirements are not as high as in previous dryers. Additionally, this drum heats-up more quickly than previous drums, since it takes far less time to heat up the electrical resistive elements 14 than it does to build up steam pressure in a boiler.

Drum 10 is more economical to use than previous drums because the heat developed by resistance elements 14 is used more efficiently than the steam heat is used in prior drums. This is true because the distance between the heating elements 14 and the exterior surface of the drum is relatively small and there is relatively little heat loss in the transfer from the wires to the materials being dried.

Finally, as was mentioned above, the ceramic or glass material used is very hard, considerably harder than either the cast-iron or steel used in previous drums. Also, it is impervious to acids and other corroding liquids so that it does not pit or corrode easily and, if it needs resurfacing at all, it does not need resurfacing nearly as frequently as previous drums. This reduces shut-down time of the manufacturing facilities and increases their production speed.

The drum 44 shown in FIGURE 2 is a modification of the drum 10 shown in FIGURE 1. Drum 44 includes a metal cylinder 46 which has a glass or ceramic coating 48 on its surface with electrical heating elements 50 imbedded in the material of layer 48. Preferably, layer 48 is a layer of material sold under the trademark Permaglas by A. O. Smith Corporation, Milwaukee, Wisconsin. Alternatively, layer 48 may be of ceramic or glass which is pre-formed into cylindrical sheet with heating elements 50 imbedded in it. This sheet may be bonded to the surface of cylinder 46 or may be secured to the cylinder by other well-known means.

A metallic rim 52 is secured to each end of sheet 48 and makes electrical contact with one exposed end of each of the resistive elements 50. Rim 52 has an angular cross-sectional shape as shown in FIGURE 2 but may have the form of a simple strip with a rectangular crosssection. It may be butt-welded or soldered to the ends of heating elements 50 or may be bonded to layer 48. In either case, it does not contact cylinder 46. A solid drive shaft 54 is secured to both ends of cylinder 46.

Electrical connection is made to resistive elements 50 by means of a pair of brushes 56 each of which is located at one end of the drum and makes contact with rim 52. Each of a pair of electrical leads 58 is connected to one of the brushes 56 and is connected to a source of alternating or direct current.

If desired, only one brush 56 and lead 58 need be used to connect one end of the heating elements to one terminal of the power supply. In such an arrangement the other end of the heating elements is connected to the metal cylinder 46 which is connected to the other terminal of the power supply through a mounting support (not shown) and shaft 54, in an arrangement similar to that shown in FIGURE 1.

The drum 44 shown in FIGURE 2 has the advantage, in addition to those cited above, of additional structural strength since the single solid shaft 54 and the rigid metal cylinder 46 are used in its construction.

The drying drum 60 shown in FIGURE 3 is an improved drum construction in accordance with the present invention. The drum itself is a standard cast-iron or steel drum 62 with a glass or ceramic coating 64 on its surface. It may be heated by steam or other known methods. A shaft 66 and other standard equipment (not shown) complete the drum structure. Preferably, coating 64 is made of Permaglas material, which is described above. It is applied directly to the surface of drum 62 during the manufacturing process. This coating is very hard and is highly resistant to pitting and corrosion. It is similar in these respects to the glass and ceramic materials described above. Since the surface of drum 60 does not easily become pitted or corroded, refinishing it will be necessary far less frequently than in previous drying drums.

In accordance with the present invention, coating 64 may be applied to used steam-heated drying drums as part of a refinishing process for such drums. First, the pitted and corroded outer surface of drum 62 is ground away and then a layer of material such as the previouslymentioned Permaglas is deposited on the surface. The surface of the coating may be polished, if desired. Alternatively, the glass layer may be laid down without first grinding the surface of the drum and the external surface of the glass coating may be smoothed and polished.

The advantage of this refinishing method is that it allows a manufacturer to put a long-lasting new finish on his existing drums and avoid buying new ones. This finish will stay smooth far longer than previous ground finishes, thus reducing much of the expense and shut-down of manufacturing operations that was previously necessitated by the frequent refinishing required.

FIGURE 4 shows a multiple-drum paper drying arrangement constructed in accordance with the present invention. A wet sheet of newly-formed paper 68 first is passed over a relatively large-diameter drum 70 which may be a Yankee drum as described above. The wet paper sheet 68 then is passed over the surfaces of a number of auxiliary drying drums 72., 74, and 76, or as many additional drums as is desired. Drums 70, 72, 74, and 76 are electrically-heated drums constructed in accordance with the present invention. For the sake of simplicity, the drums shown in FIGURES 4 and 5 are illustrated as being of the type shown in FIGURE 1.

Positioned near the outer surface of the drums shown in FIGURE 4 are curved housings 78, 80, 82 and 84. As is well-known, these housings contain means for heating the outside surface of the paper to the same temperature as that of the surface contacting the drum so as to promote uniform drying. In addition, they may contain an exhaust system for removing the evaporated liquids from the region near the surface of the paper so as to hasten its drying.

Thermostatic heat-sensing control elements 86, 88, and 92 are positioned, respectively, near the outside surface of drums 70, 72, 74 and 76. These thermostatic elements sense the temperature of the drum near the position at which the paper first contacts the drum.

FIGURE 5 shows the electrical connections for the drums shown in FIGURE 4 and their thermostatic elements. Bearing-blocks 94 of these drums are connected to one power line 96 and bearing-blocks 88 are connected to the other power line 100 through their thermostatic control elements.

An advantage of the FIGURE 5 arrangement is that the temperature of each drum may be controlled individually and changed quickly by means of its thermos-tat. In contrast, in prior steam-heated drying drum arrangements it is diflicult to accurately control the temperature of each individual drum and the process of changing the temperature of each drum is slow. The arrangement in FIGURE 5, is therefore, substantially faster-acting and more flexible than previous arrangements.

The above description of the invention is intended to be illustrative and not limiting. Various changes or modifications in the embodiment described may occur to those skilled in the art and these can be made without departing from the spirit or scope of the invention as set forth in the claims.

I claim:

1. Apparatus for drying wet sheet paper, said apparatus comprising, in combination, a rotatable drum having a smooth, substantially continuous external surface member of electrically insulating material, said material being selected from the group consisting of glass and ceramic materials, a plurality of electrical heating conductors imbedded in, surrounded by, and separated from one another by said material in said surface member, means for conducting electrical energy from a source of electrical energy through each of said conductors, and means for rotatably mounting said drum and rotating said drum in response to the output of a rotary drive power source.

2. Apparatus as in claim 1 in which said energy conducting means comprises a pair of conductive stators each of which contacts one of a pair of conductive rotors each of which contacts one end of each of said imbedded conductors.

3. An electrically-heated drum for drying sheet paper, said drum including a metallic cylinder, a layer of electrically non-conductive material selective from the group consisting of glass and ceramic materials on the surface of said cylinder, a plurality of electrical heating elements imbedded in the material of said layer near its exterior surface with the ends of said heating elements being exposed at each end of said layer, at least one electrically conductive member contacting one end of each of said heating elements, said conductive member being positioned so as not to contact said metallic cylinder, stationary means for making electrical contact with said conductive member and conducting electrical current from an electrical power supply through said heating elements, and

means for rotatably mounting said drum and rotating said 4 drum in response to the output of a rotary drive power source.

4. An electrically-heated drum for drying sheet paper, said drum including a metallic cylinder, a layer of electrically non-conductive material selected from the group consisting of glass and ceramic materials on the surface of said cylinder, a plurality of electrical heating elements imbedded in the material of said layer near its exterior surface with the ends of said heating elements being exposed at each end of said layer, at least one metallic rim contacting one end of each of said heating elements, said metallic rim being positioned so as not to contact said metallic cylinder, a stationary, electrically conductive brush contacting said rim, said brush being adapted to be connected to an electrical power supply and to conduct electric current from said supply through said heating elements, and means for rotatably mounting said drum and rotating said drum in response to the output of a rotary drive power source.

References Cited by the Examiner UNITED STATES PATENTS 1,433,674 10/ 1922 Carl 219-471 1,497,223 6/ 1924 Moodie 219-469 X 1,955,508 4/1934 Lofman 219-244 2,038,607 4/1936 Sauer 219-457 2,150,929 3/1939 Kohler 117-2 2,326,044 3/1943 Littleton -89 X 2,409,244 10/1946 Bilan 219-457 2,43 0,920 11/1947 Dodge 219-244 X 2,526,906 10/1950 Schaab et al. 219-469 2,552,259 10/1951 Collins et a1 219-469 X 2,622,038 12/ 1952 Charlesworth et al. 117-2 2,679,572 5/1954 Workman 219-469 2,680,468 6/1954 Lewis 219-244 X 2,700,094 l/1955 Hosack 219-316 2,870,312 1/1959 Westerwelt 219-244 2,831,097 4/1958 Malewski 219-470 3,012,141 12/ 1961 Thomiszer 34-123 3,169,729 6/1965 Lusebrink 219-469 FOREIGN PATENTS 1,157,100 12/1957 France.

631,618 1/1937 Germany.

693,659 7/ 1940 Germany. 1,110,777 7/1961 Germany.

246,319 3/ 1926 Italy.

ANTHONY BARTIS, Acting Primary Examiner.

RICHARD M. WOOD, Examiner.

V. Y. MAYEWSKY, Assistant Examiner. 

1. APPARATUS FOR DRYING WET SHEET PAPER, SAID APPARATUS COMPRISING, IN COMBINATION, A ROTATABLE DRUM HAVING A SMOOTH, SUBSTANTIALLY CONTINUOUS EXTERNAL SURFACE MEMBER OF ELECTRICALLY INSULATING MATERIAL, SAID MATERIAL BEING SELECTED FROM THE GROUP CONSISTING OF GLASS AND CERAMIC MATERIALS, A PLURALITY OF ELECTRICAL HEATING CONDUCTORS IMBEDDED IN, SURROUNDED BY, AND SEPARATED FROM ONE ANOTHER BY SAID MATERIAL IN SAID SURFACE MEMBER, MEANS FOR CONDUCTING ELECTRICAL ENERGY FROM A SOURCE OF ELECTRICAL ENERGY THROUGH EACH OF SAID CONDUCTORS, AND MEANS FOR ROTATABLY MOUNTING SAID DRUM AND ROTATING SAID DRUM IN RESPONSE TO THE OUTPUT OF A ROTARY DRIVE POWER SOURCE. 